1. Field of the Invention
This invention relates to a radio paging system in which paging signals are broadcast from a base station to a plurality of pagers by way of radio channels and, more particularly, to a paging system in which the identification number (ID) codes of pagers are effectively transferred.
This invention further relates to a radio system such as a paging system, a cellular radio system, or a cordless telephone system wherein a base unit addresses a particular radio mobile unit by transmitting an identification signal which is identical to an identification code stored in a memory unit of the radio mobile unit and more specifically to a method of rewriting the identification code stored in said memory unit.
2. Description of the Related Art
Hitherto used as a communication system is a radio paging system comprising a base station, paging exchanger, and pagers. In this system, a request for any desired one of the pagers is sent from a telephone line to the base station through the paging exchanger. Upon receipt of the paging request, the base station forms a paging signal containing the identification number (ID) code of the desired pager. The base station broadcasts the paging signal at the time assigned to the group of pagers, including the desired pager.
FIG. 1 schematically illustrates a pager which can be used in the radio paging system. As is shown in this figure, the pager comprises antenna 1, a radio circuit 2, demodulation circuit 3, code-collating circuit 4, ID memory 5 such as a ROM, EPROM, EEPROM, drive circuit 6, speaker 7, and memory receptacle 8. In operation, antenna 1 catches a paging signal broadcast by the base station (not shown). Radio circuit 2 receives the paging signal from antenna 1. The paging signal is demodulated by circuit 3, and is then supplied to code-collating circuit 4. Circuit 4 collates the ID code inserted in the paging signal, with the ID code stored in ID memory 5 and representing the ID number of the pager after performing error correction operation. When the ID code inserted in the paging signal is identical to that stored in ID memory 5, circuit 4 supplies an alarm signal to drive circuit 6. In response to the alarm signal, circuit 6 drives speaker 7. As a result, speaker 7 makes a beep sound, informing the user of the pager that he or she is being called.
FIG. 2 illustrates another pager which can be used in the radio paging system. This pager is different from the pager shown in FIG. 1 in two respects. First, code-collating/message-processing circuit 4' is used in place of code-collating circuit 4. Secondly, it further comprises a display D such as a liquid-crystal display. In operation, when circuit 4' determines that the pager is being requested, not only speaker 7 makes a beep sound, but also the display D displays the message, such as the caller's name and telephone number, which has been obtained by decoding the message code inserted in the paging signal broadcast from the base station (not shown).
When the user uses the pager illustrated in FIG. 1, he can know that he is being called, upon hearing speaker 7 making a beep sound. When he uses the pager shown in FIG. 2, he can know who is calling and what is the caller's telephone number, upon seeing the message on the display D.
ID codes are assigned to either type of a pager, described above. The ID code must be altered in some cases, for instance when the pager changes hands. To facilitate the alteration of the ID code, ID memory 5 can be detached from the memory receptacle 8. When it is necessary to alter the ID code, ID memory 5 is removed from receptacle 8. The ID code is altered, either by inserting another ID memory storing the new ID code, into memory receptacle 8, or by inserting the ID memory 5 back into receptacle 8 after the ID code has been rewritten by means of external ROM writer 9.
Obviously, the ID memory 5 must be a detachable DIP-type package which includes a relatively large ROM and is thus a relatively large, and the memory receptacle 8 for accommodating ID memory 5 inevitably occupies a large space. This is greatly detrimental to miniaturization of the pager and reduction in the number of components. The pagers shown in FIGS. 1 and 2 are inevitably large.
In order to alter the ID code, the user must open the case (not shown) of either pager described above, must draw ID memory 5 from receptacle 8, and must insert ID memory 5 or a new ID memory into receptacle 8. It takes him rather much time to open the case, draw memory 5 from receptacle 8, and insert memory 5 or a new ID memory into the receptacle.